AP1000 Pressure Vessel Flange Organization And Performance Evaluation Took Forgings

In this work, the properties of a flange welded pipe forging from API000pressure vessel produced by a domestic plant were comprehensively evaluated, according to the requirements of major special project mission statements as well as the ASME standards for the properties evaluation of SA508-3steels. On the basis of a throughout research about the references and standards home and abroad, specimens from the different positions of the cross section of the forging riser and outlet were selected to get an exhaustive knowledge about the properties of the domestic forgings. Elemental analysis, tensile tests at room temperature and350℃as well as impact toughness tests were conducted. The ratings of non-metallic inclusions and grain size as well as the detailed observation and analysis of micro structure were done by means of optical microscopy (OM), scanning electron microscopy (SEM) as well as transmission electron microscopy (TEM). In combination of the continuous cooling transformation (CCT) curves determined by dilatometer and the actual cooling procedure of the domestic forging steels, the differences in microstructure and properties of the specimens at different positions of the cross section were briefly discussed and the following conclusions were drawn.(1) The chemical composition and rating of non-metallic inclusion standard were satisfied at the required testing position according to the ASME requirements.(2) The room temperature tensile strength (550-725MPa、RpO.2>345MPa) and high temperature (350℃)tensile strength (Rm>505MPa> RpO.2>345MPa) and impact toughness (>48J) were satisfied according to the ASME requirements.(3) By OM observations of the specimens from different positions of cross section (TO/4, T/4, T2/4, T3/4, T4/4), it is found that the microstructure of inner and outer surface (TO/4, T4/4) was the mixture of granular bainite and little martensite. The ferrite and carbides inside the bainite microstructure were small in size. On the other hand, the microstructures at the quarters and center of cross section were fully comprised of granular bainite. The carbides preferentially locating at the original austenite grain boundary were large in size. (4) The CCT curve of the domestic forging indicated that, with the decrease of cooling speed, the microstructure of SA508-3steels transformed from martensite to bainite and finally to ferrite, while during the cooling procedure, mostly mixed microstructure. Owing the difference in cooling speed at different positions of cross section, the uneven in microstructure and properties was found in the fringe forgings.The microstructure and mechanical properties at different positions of cross section of domestic fringe pipe forging of AP1000pressure vessel were investigated. The industrial data feedbacks were gathered for the laboratory studies. Reliable data were provided for the domestic AP1000RPV forging property database and the localization process for AP1000RPV forging was enhanced.